Novel methodology to evaluate displacement efficiency of drilling mud using fluorescence in primary cementing

For primary cementing of a well, successful displacement of drilling mud from the casing and annulus, and properly conditioning those surfaces to bond with the cement slurry, are paramount to achieve zonal isolation. In this study, to evaluate displacement of drilling mud from well casings, a fluorescence methodology incorporating a hydrophobic dye was developed. Fluorescence is attractive because the dye is highly oil soluble and non-polar and can be detected at very low concentrations, so chemical interference between dye and drilling mud is minimized. From the fluorescence measurements, the thickness of residual drilling mud can be quantitatively determined, which makes it possible to quantify the efficiency of drilling mud removal. Residual oil layers under consideration in this study from 32 μm to 1.5 μm are observed. The spacer fluids D and E are excellent in their ability to remove the drilling mud, whereas spacer F performs poorly. The effects of metallurgy and surface roughness on wettability were investigated using the measured thickness of residual drilling mud. There is little effect of the composition of the steel tube on wettability, but the surface roughness or presence of corrosion can significantly affect the wettability.